How can a catch a wild turtle?

ok u need a simple way to catch a wild turtle with out going in the water.the pond im going to catch from is in a cow field so there for to nasty to swim in or for that matter touch i need somethin simple that is for sure going to catch me a turtle or two.and people please dont answer this saying its illegal or dangerous cause i live in TN and its not illegal and i need them out because they are snapping turtles and keep bitting the cows feet and we are affraid they could get infected/sick walking in the nasty water with cuts on them...also i need a trap i can easily build at home and cheap too..thanks and please answer ASAP!